How to maintain multiple cameras with different resolutions
This kind of situation is best handled with Python in my opinion since it's so simple to tweak and you can keep working on just one scene.

This simple script would change scene resolution, change camera (perspective/orthographic views are set within the camera), and start the render:

import bpy

bpy.context.scene.render.resolution_y = 1110
bpy.context.scene.render.resolution_x = 870

bpy.context.scene.camera = bpy.data.objects['camera1']
bpy.data.scenes['Scene'].render.filepath = "C:/Test/"+"orthographic"
bpy.ops.render.render(animation=False, write_still=True, use_viewport=False)

bpy.context.scene.render.resolution_y = 220
bpy.context.scene.render.resolution_x = 360

bpy.context.scene.camera = bpy.data.objects['camera2']
bpy.data.scenes['Scene'].render.filepath = "C:/Test/"+"perspective"
bpy.ops.render.render(animation=False, write_still=True, use_viewport=False)


To use make sure you change the resolution numbers, match the camera object names, change camera object to perspective or orthographic, match the 'Scene' to the name of your scene, change the filepath C:/Test/ to wherever you want to render.